5D3 coming. Advice?

If you have a partner, give them some attention, becuase when the camera comes they will soon get fed up with you fiddling with it the whole time, taking pictures and not listening to them.

The thing with a 5D3 type camera is that there are so many customisations and settings you really need to make use of the custom settings on the main dial. Think about your three most common shooting situations and dial in all those custom seetings to match each of those three situations on your three dial positions. That way you will be spending less time configuring things when you really need to be shooting. The button customisation is really useful in this regard (AF ON , DoF Preview e.t.c.).